This invention relates to an apparatus devised to aid the heart in its contractile function.
The object of the invention consists in an apparatus to treat cardiac insufficiency through a system similar to the physiologic way, improving heart emptying, allowing to initially and, in further controls, regulate contractility and distention parameters as well as cavity filling and emptying times fitting the mechanics to the heart electric activity and keeping a physiologic way because the apparatus aids the heart in its own operation working in a similar way to the systolic contraction of the physiologic ventricular and atrial musculature.
The apparatus of the invention allows to improve the contraction of heart cavities in global dilatations (in the typical case of dilated cardiomyopathy) as well as the contraction of segmentary dilatations, so also asynergies, dyssynergies, aneurysms and zonal dilatations of many cardiopathies can be prevented.
Cardiac insufficiency in its concept of incapacity for the heart to meet its blood pumping function is a frequent state to which one can be lead by several causes and mechanisms.
It is the cause of physical impairment, functional incapacity and a situation of illness in many thousands of persons, and it is the mechanism which leads a great number of patients to death.
Many attempts have been made to try to overcome or to relieve cardiac insufficiency, and during last years, the advances are considerably great because of the always better knowledge of the heart physiologic and pathologic mechanisms as well as those of the rest of the organs and systems which are involved in its operation, as well as the progress of diagnostic and therapeutic techniques in their pharmacologic, mechanic and electric features.
All of it leads to an important advance in the treatment of cardiopathies with subsequent improvement of survival, quality of life and in the relief or disappearance of the symptoms and complications to which cardiac patients are exposed.
However, the field in which advances have still to be made is very large. The evolution of the cardiac insufficiency is attenuated with drugs and final failure is significantly delayed compared with former times, but still we are not capable to prevent it nor to provide the myocardium with the lost strength when it reaches a certain degree of dilatation and diminution of its contractile capacity.
It is so to such extent that, during last decades a number of heart transplantation units have been developed to provide with a new heart from somebody else patients whose prognosis was unfortunate because the rest of the medical possibilities were exhausted to stop the evolution towards definite failure in a weakened heart.
Artificial hearts have been also developed which include a pumping system in the apparatus itself. But said artificial hearts, because of the haemolysis they produce and other important medical drawbacks and high economic costs, up to now, are not long lasting and in many cases they are applied temporarily while the patient is waiting for a heart transplantation.
The Revista Espaxc3x1ola de Cardiologxc3xada, vol. 51, pages 23-30, July 1998, publishes an article by Dr. Francisco Torrent Guasp, where a contention prosthesis is disclosed which consists in a stiff or malleable non extensile ring which carries out a contention task in the ventricle two basal thirds, narrowing the ventricular mass. Said contention prosthesis would limit a further heart dilatation but would not allow to regulate the diastolic volume nor would make further modifications possible and it wouldn""t improve systolic emptying. Said article includes a description and illustration of the ventricular mechanics in the function of which four main ventricle motions are distinguished: narrowing, shortening, lengthening and enlarging (FIG. 3, page 522).
Patent U.S. Pat. No. 5,383,840 discloses a biocompatible device for ventricular aid and arrhythmia control including a compressing assembly which comprises a band for wrapping the heart perimeter and means to more or less closely fit the band around the external walls of the ventricular cavities during predetermined periods of time so that a pressure is applied to said ventricles which is approx. transversal to the lengthwise axis thereof, of an adjustable value, in synchronism with the systolic cycles of said cardiac cavities, in addition to the cavity walls narrowing-shortening and said means allowing further loosening and dilatation of said walls chronologically with the cardiac cycle.
Said patent discloses in details other systems of the state of the art applied to same aim among which the patent U.S. Pat. No. 4,304,225 is referred to which also discloses a pressure band.
Other documents of the state of the art relative to the object of this invention are disclosed in patent U.S. Pat. No. 4,448,190 which includes a wrapping associated to pumping means to closely fit or loosen an organ such as the aorta or the ventricles while a series of electrical impulses are sent in synchronism. Another similar device appears disclosed in patent U.S. Pat. No. 5,131,905.
In all these backgrounds the devices compress the heart transversally, as if a manual massage was performed. This way of compressing, in spite of being effective, is different of the physiologic behaviour in the systolic contraction of the ventricular muscle, which expels the blood from the apex to the base of the ventricles.
On the other hand, none of mentioned backgrounds foresees means for applying a contractile treatment similar to that of the atria and to allow treating simultaneously or separately atria and ventricles.
Unlike mentioned backgrounds, the invention proposes an apparatus aiding physiologic systolic and diastolic dynamics of the heart cavities which we will call SPES (system for pressing electrosyncronically) for aiding the heart in its contractile function.
The apparatus consists in a stable structure or wrapping, acting as a receptacle, having a contour similar to that of the ventricles, approximately cone-shaped, and which surrounds/sheathes them, the mouthpiece of which includes a first stiff ring which the same as a distal tip of the structure, distal from the ring and on which the heart apex will be arranged, is fixed to the body skeleton (ribs) for example with flexible tension members or semi-stiff members having the suitable texture which guarantee its relative locking.
Coupled to said first stiff ring, there exists a second stiff ring, having a slightly smaller diameter, guided with possibility to concentrically revolvingly slide, a driving device having been provided fixed to the external ring and with a toothed member geared with a peripheral toothed profile of the external wall of the internal ring, so that when said motor acts the internal ring is revolvingly moved, sliding driven on the external ring which remains fixed.
An approximately cone-shaped bag of flexible fabric, similar to the ventricular contour is connected by its mouthpiece to the rotating internal ring, above described, and its vertex is internally joined to the distal tip of the external stiff wrapping.
By means of said arrangement, said flexible internal bag remains in contact with the pericardium which wraps the ventricles, containing the heart within it and in turn surrounded by said stiff structure integral with the external ring in such a way that the apparatus squeezes the internal bag when the internal ring rotates.
That is to say, the behaviour of the apparatus which is proposed acts according to the heart physiology of systolic contraction of the ventricular musculature, carrying out an emptying upward the aortic and pulmonary valves, which results particularly effective for systolic emptying as emptying direction is the same as that of the myocardium at the systole.
The structure, surface and distribution of said bag fibres will be selected so that they allow to apply different pressures on one or the other ventricle.
The apparatus includes in addition:
control means to remote monitoring, during the operating periods, the application of rotations in one or the other direction of the internal ring, in synchronism with the physiologic cardiac dynamics which comprise:
a driving system;
a battery or power supply for the driving system;
a regulating system; and
means to keep the external ring and the distal tip of the stiff structure distal thereof fastened on the thorax so that said structure is arranged around the heart in such a way it cannot be taken away.
According to a preferred embodiment of the invention, the apparatus includes a cap which is placed on the atria adapting itself to their contour and having care of the incuts of the caval and pulmonary veins which converge on them. This cap is joined by means of tension members which have a toothed profile sector and which are geared in a controlled way with driving toothed wheels located on the external face of the stable/stiff structure which wraps the ventricles or in the external ring.
The anatomy of the atria and their topographic relation with the large vessels do not allow to so easily closely fit them by means of a bag or sheath similar to the one proposed for the ventricles, therefore the atrial system will consist in a cap surrounding them.
Said cap must have a shape which can be adapted to the atrial external surface, with the suitable incuts at the area joining them to the vessels so that these latter are not compressed when constricting the atria.
This cap can be narrowed and lead downward in cranio-caudal direction by means of tension members having a toothed profile associated to driving toothed wheels which are supported on the apparatus external wrapping or external ring.
The rotation of said wheels will make the atrial cap go downwards the ventricles, compressing the atria and obliging them to empty themselves and to provoke atrial emptying through the mitral and tricuspid valves or to go up and decompressing them, allow the atrial diastole.
If the system is only an atrial system, a protecting sheath will wrap the ventricles with the aim of preventing the friction produced by the tension members and of providing a support for the driving system.
If the system is double, i.e. atrial and ventricular, the tension members of the atrial module and its closing mechanism will be external with respect to the ventricular module (external stable structure) to also prevent that its motion damage the heart surface.
The apparatus can be arranged surrounding only the ventricular part with which only the ventricular diastole and systole will be controlled.
It can be also arranged around the atria controlling atrial diastole and systole.
When wished, both systems will be matched although it has to be quite clear that the wrapping parts are specific for one and the other cavities, the atrial systole, the atrial diastole, the ventricular systole and the ventricular diastole being in said case regulated in a sequence identical to that of the heart cycle physiology.
A significant advantage of the apparatus proposed is that it is placed on the external surface of the heart. Thus it does not contact the intracavitary blood so it does not damage the blood cells as do present artificial hearts above mentioned and unlike the alternative systems of cardiac aid disclosed in mentioned patents, it provokes a physiologic action and makes an application on the atria possible, independent from or combined with the treatment of the ventricles.
Operating mechanisms: A) Ventricular mode
Coinciding with the ventricular systole, the internal ring, base of the flexible bag, rotates around its center, driven by the driving system. As the internal cone vertex remains fixed on the external structure and therefore cannot move, when its base rotates, the walls are constrained and oblige the ventricles, contained within them, to empty themselves, doing it in same way as the heart is physiologically emptied. The blood contained within them will be emptied toward the cone base which is the place where the sigmoid valves (aortic and pulmonary) are located and will be poured toward the great vessels (aorta and pulmonary artery).
The more degrees the internal ring rotates, the greater will be the cone narrowing, lower the volume contained and larger the amount of blood expelled in the systole of the ventricles toward the great vessels, i.e., more are we increasing the so-called xe2x80x9cventricular ejection fractionxe2x80x9d.
Time wished for each period of constriction to achieve a suitable emptying will be determined for each case.
Once the systole period ends, the ventricles must relax to be able to be filled in the diastole.
When rotation occurs in the opposite direction to the above mentioned, the flexible fabric bag which wraps the ventricles comes back to its former shape, recovers the capacity, larger when the ring is rotating more around it in its return, and allows that the ventricles, contained within it, relax in diastole, and are filled with the blood coming from the atria.
To this aim, at the scheduled moment, the internal ring is caused to rotate in the opposite direction to the former and wished diastolic volume will be achieved. If it is wished to recover the maximum possible diastolic volume, the return will be total, coming back to the position in which the internal cone has its maximum volume.
If in a patient it is wished to diminish the diastolic filling, the return will be adjusted so that the internal ring rotates less degrees preventing thus an excessive diastole filling.
The possibility to adjust the amount of ring return up to its primary position likewise offers the capacity to determine which will be the maximum ventricular relax we wish to allow and therefore to adjust the diastolic volume according to our wish.
This allows in addition to reduce or eliminate the excessive heart distension, that means, the diastolic congestion, which is a very important factor in cardiac insufficiency when the ventricles have exceeded a critical degree of dilatation.
Also the time it is wished for each period of relax will be determined to achieve a suitable filling in each case.
Thus the possibility to adjust the rotation in one direction or the other leads to regulate with it at our will the systolic volume and the diastolic volume and to fight so the two main components of cardiac insufficiency: insufficient contractility and excessive dilatation.
B) Atrial mode
In many cases, the patients are in atrial fibrillation. Up to now, the single medical actions for this situation consist in:
1) trying to recover the sinus rhythm with drugs or electrical cardioversion
2) controlling with drugs the ventricular frequency of a permanent fibrillation
3) some times, to carry out the ablation of the atrio ventricular conduction when ventricular response cannot be controlled.
In other cases, although the patient is in sinus rhythm, there are atrial dilatations which would take profit of a mechanical aid for their emptying.
With the system we propose, it can be tried to squeeze the atria in a way similar to the atrial systole which, in cardiac cycle, coincides with the last part of the ventricular diastole.
This means three important advantages:
1) it is taken profit of the percentage in which the atrial contraction contributes to cardiac output;
2) atrial dilatation is prevented;
3) as its emptying is kept it is prevented that blood clots are formed within it, with subsequent risk of pulmonary or systemic embolisms.
If the patient has a sinus rhythm of his/her own and it is wished to aid the atrial systole, when the P wave of the electrocardiogram appears a rotation will be provided of one toothed wheel which has to pull down the cap wrapping the atria.
This rotation can generate in said cap a displacement parallel to the larger heart axis, so they would be only moved downward. But if it is wished, providing the tension members which fasten said cap with a determined inclination on said larger axis, it would be achieved that when the toothed wheel rotates, a certain degree of twist occurs, having always care that the twist is not such that it chokes the atrial great vein entrances.
Implantation and Fastening
Initially and while the system technical evolution does not allow another procedure, placing will occur with a surgical operation with thoracotomy.
The apparatus wrapping the heart will be placed outside the pericardium. Bearing in mind that the heart and the anatomic tissues which surround it (lungs, great vessels and all the mediastinal structures) frailty prevent that they are surgically fixed on them, said apparatus must be fixed on stronger nearby structures, the anatomy and function of which will not be damaged with the proper motion of the apparatus. As it was mentioned, the external ring and the external wrapping tip are fixed on the ribs to prevent apparatus twists and displacements and at same time to provide stability and support for the system operation.
In the surgical act of implantation, the other end of each tension member of flexible material will be fixed on itself surrounding a rib at the best suited point nearby, so that it does not damage nervous or vascular structures.
It will be convenient that several tension members fasten the apparatus external ring and that one or several fasten the distal vertex.
The number of tension members will be sufficient to have the apparatus tightly fastened on the chest. Their width will be suitable in order the motion does not damage the ribs on which they have to be fastened. The length will be according to the sizes of the apparatus and, last, in the surgical act, the surgeon will determine which length of each tension member has to be bent on itself and be stitched with suture in order it offers suitable stability without distorting the anatomy of the region by provoking unsuitable angles. Alternatively to the tension members, one or more semi-stiff members having suitable profile may be used.
In order the heart remains fastened within the apparatus, tension-memberlike girths having a system similar to that of the suspender of a trouser, can be passed over the heart, leaving it wrapped and, by means of a closing system, which can be with surgical stitches or otherwise, be fastened on the apparatus itself, and so prevent that the apparatus is displaced or the heart goes out of it.
The system has the advantage that the apparatus can be easily withdrawn later on in the event the same patient has to suffer a surgical operation on the heart, for example, to make an aorto-coronary by-pass or for the possible case that any circumstance makes advisable to renew the apparatus.
Power supply and conduction system
The ideal power supply system will be a large capacity battery type generator which allows to implant it within the organism of the patient, periodically renewable, as it is done nowadays with the pace-maker generators. This will have the advantage not to depend on an external power supply which requires a connection between outside and inside the organism.
If in principle power requirements do not allow that the battery is internal, a transthoracic cable may connect the apparatus motor to the power supply which can be external batteries the patient bears in an haversack as presently do those bearing an artificial heart.
Chronological regulation with relation to the electric cycle of the control system
An electronic generator, similar to that of a pace-maker and which will be implanted within the organism of the patient in same surgical act, will be the one that will send to the driving system the impulses to start the contraction and distension.
Also from it will be determined:
a) the moment of starting the contraction
b) the duration of the contraction
c) the amount, speed and duration of the rotation of the ring for the contraction
d) the moment when the distension begins
e) the duration of the distension
f) the amount, speed and duration of the rotation of the ring for the distension.
To keep a suitable sequence in the contraction of the cardiac cavities and to keep the physiologic periods of filling and emptying, it is required to adjust the mechanical activity to the electrical activities of the heart, respecting the periods of isovolumetric contraction, emptying, isovolumetric relaxation and filling.
A sensor similar to the cable of a pace-maker will detect the beginning of QRS ventricular complex of the electrocardiogram in order that, same as for the physiological ventricular systole, it is it that determines the beginning of the constriction and assist to ventricle systolic emptying when it is sought to start the ventricular module.
The same sensor or another similar will have to detect the P wave of the electrocardiogram when the atrial module is to be used.
If the ventricles are stimulated by a pace-maker, the ventricular spicule will be the detonative of the beginning of the start of the rotation for the ventricular systole.
If it is an atrial mode and the patient has no atrial rhythm of his/her own with detectable P wave, a pace-maker in atrial or bicameral mode will be which will awake the atrial mode from the spicule of the atrial cable.
Regulation in further controls
Just as it can be done with a pace-maker, these parameters may be controlled and readjusted from outside as many times as it is wished to obtain an optimum performance in each patient.
Clinical and radiological controls and more accurately echocardiographic controls will show the state of each patient and the adjustments to perform each time.
Driving mechanism
An adjustable rotor will be the driving element of the ventricular contraction system. The rotor connected to the battery and to the regulation system will do that the internal ring rotates during the systole as many degrees as it is scheduled in order to achieve the wished systolic expression and to aid the ventricles to be emptied.
The rotation in opposite direction of this rotor will do that the cone delimited by the internal bag increases the capacity in the diastole in order that the ventricles are filled in the amount scheduled to obtain a best hemodynamic performance.
The motor may be fixed to the apparatus external ring which will keep it stable with relation to the heart. The very best location on said ring or wrapping casing will be depending on the occupied spaces, trying that its opacity does not interfere in further scanning in echocardiographic controls which have to be carried out for patient follow-up and suitability of the apparatus operating parameters.
As the external wrapping (external ring and distal tip of the wrapping) have been fixed on the chest by means of the tension members above mentioned in the fastening system, the apparatus and the motor will remain thus stable on the thorax and suitably wrapping the heart.
They can be arranged surrounding only the ventricular part so that only the ventricular systole and diastole will be controlled.
Also a cap can be applied around the atria controlling the atrial systole and diastole.
In the events when it is wished, both system will be matched and synchronizing the mechanisms the atrial systole, the atrial diastole, the ventricular systole and the ventricular diastole will be regulated in identical sequence to that of cardiac cycle physiology.
An explanation of the apparatus of the invention is given below on the ground of the examples of embodiment thereof which are illustrated in drawings attached which have to be taken as illustration and not a limitation to the scope of the invention.